Autogenous grinding mill



Dec. 27, 1966 J. E. NELSON 3,294,325

AUTOGENOUS GRINDING MILL Filed Sept. 20, 1965 5 ShGBtS-ShGGt l a 5; 54 a 3 2 r 5 r s \-1 Q FJ5.Z. E X"\ A) INVENTOR. JOHN E. NELSON Dec. 27, 1966 J. E. NELSON AUTOGENOUS GRINDING MILL 5 Sheets-Sheet 2 Filed Sept. 20, 1963 DIE'EICTIO N OF ROTATION INVENTOR.

N E L S O jfi ATTOPNEK JOHN E.

Dec. 27, 1966 J. E. NELSON AUTOGENOUS GRINDING MILL 5 Sheets-Sheet 5 Filed Sept. 20, 1963 8 3 10 4 5 W at 4 m i 5 4 m u m 4/ v l M V 4 2, F W h 4 4 1. f

INVENTOR JOHN E NELSON United States Patent 3,294,325 AUTOGENQUS GRINDING MILL John E. Nelson, Montreal, Quebec, Canada, assignor to Dominion Engineering Works, Limited Fiied Sept. 2%), 1963, Ser. No. 310,272 1d Claims. (Cl. 241-70) This invention relates to autogenous grinding mills or the like and has particular reference to the provision of a new and improved autogenous grinding mill which is partifularly adapted for operation upon run-of-mine materia As used herein, the term autogenous shall mean the use of the friable material undergoing reduction, either in whole or in part, as its own grinding media. The term run-of-mine material, as used herein, shall mean a mixture of friable material which normally includes coarse, intermediate, and fine sizes, the larger sizes being sufficient to eifect self reduction and reduction of the other sizes present in the material.

Conventionally, autogenous mills adapted to accept runof-mine material are of two types. The first of these types is characterized by the fact that it employs a grinding chamber that, in shape, is essentially cylindrical bounded by plane ends. The other of said types is characterized by the fact that it employs a grinding chamber that, in shape, comprises, essentially, a central cylindrical section bounded by conical ends.

Grinding chambers of these shapes however, fail to make optimum use of the maximum possible volume and dimensions involved, and, further, due to their foredescribed shapes, require that discharge grates therein be comprised of expensive materials such as, for example, manganese steel or chrome-molybdenum steel.

An object of the present invention is to provide a new and improved autogenous grinding mill for run-of-mine materials which includes a grinding chamber that is so constructed as to make optimum use of the volume and dimensions possible and which is, hence, more efiicient than conventional mills.

Another object of the present invention is to provide a new and improved autogenous grinding mill of the type set forth which is more economical in construction than conventional mills.

Another object is to provide a new and improved autogenous grinding mill of the type set forth that includes a grinding chamber that is so constructed that the discharge grates therein can be constructed of a more inexpensive and harder material than is possible in conventional mills of this type.

Furthermore, the autogenous grinding mill which is provided herein is provided with the form of discharge which is known as a grate discharge and which permits the operation of the mill with either a wet or a dry material.

The present invention provides an autogenous grinding mill of compound cylindrical form, having a central cylindrical portion and axial end walls comprising a plane outer annular portion combined with an axially outwardly extending conical inner portion.

The grates comprising said grate discharge may have openings that are either slotted, circular, or of other shape for limiting the size of the discharge from the mill or may be constructed with ports larger in size than any required size of discharge, in which latter case the control of the size of the mill product is accomplished elsewhere. Furthermore, the grate sections may, in some cases, be comprised of non-perforated cover plates.

With this form of mill discharge, it is necessary to pro vide a means for elevating the ground material from the periphery of the mill, behind the grates, to a point close to the center line of the mill for discharge. The means Patented Dec. 27, 166

which are generally utilized for this purpose are lifters comprised of flat, radial surfaces interposed between the grates and the discharge head of the mill.

It is an object of the present invention to provide .a new and improved autogenous grinding mill which includes means for the separation of the discharge of the mill into two or more separate and distinct products.

It is another object of the invention to provide a new and improved autogenous grinding mill of the type set forth which includes means for such separation, which means also facilitates the return of unwanted portions of the mill discharge to the mill for further grinding without the necessity that external auxiliary apparatus be employed in said return.

Another object is to provide a new and improved means of the type set forth which utilizes perforations in the lifters for such separation and return.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings. It will be understood that changes may be made in the details of construction and arrangement of parts shown and de scribed as the preferred form of the invention has been given by way of illustration only.

Referring to the drawings:

FIG. 1 is a sectional view of a primary autogenous mill grinding chamber constructed in accordance with the present invention;

FIG. 2 is an enlarged view of that portion of FIG. 1 shown encircled;

FIG. 3 is a fragmentary diagrammatic sectional view of the size and product separation portion of the autogenous mill;

FIG. 4 is a sectional view through the trunnion illustrating a means for the discharge of two or more pockets of the mill to two separate delivery points; and

FIG. 5 is a view taken on line 5-5 of FIG. 4 looking in the direction of the arrows.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, the device illustrated in FIGS. 1 and 2 comprises a grinding chamber 29 for an autogenous grinding mill 14 which is adapted to operate upon run-of-mine material. Said grinding chamber comprises, essentially, a central cylindrical section 29a, having ends 54 which are plane for a portion of the distance from the periphery towards the axis of the mill 14; from that point inward, said ends being of conical shape.

As a result of this foredescribed construction of the grinding chamber 29, the use of composite end walls permits the cylindrical central section 54 to be of greater axial extent, for a mill of given length, which provides for a greater axial width zone of unhampered fall of material at the maximum working diameter where the self grinding action is most effective. At the same time, the necessary strength and rigidity is provided by the modified end walls.

Furthermore, also as a result of this foredescribed construction of said grinding chamber, the discharge grates 32 are enabled to be positioned where they are substantially protected from the direct action of the material which, in the operation of the mill 14, is tumbling within grinding chamber 29. Because of this location of said grates 32 in a self protecting position in said grinding chamber, coupled with the provision of an annular liner ring 30 adjacent to the inner periphery of the grates 32, at the juncture thereof with the conical portion of the end walls said grates may be fabricated from a harder and less expensive material than is conventionally possible. By way of specific example, in a grinding chamber 29 constructed in accordance with the present invention, the discharge grates 32 may be constructed of hard, but relatively brittle, Ni-Hard iron, while, in conventional grinding chambers, said discharge grates must be constructed of either manganese steel or chrome-molybdenum steel.

Details of the positioning of one of the discharge grates 32 provided by the present invention are shown in FIG. 2. Said discharge grate, as shown in FIG. 2, is positioned in a protected position in grinding chamber 29 due both to the shape of said chamber and, also, to the provision of the protective liner 30. In FIG. 2, furthermore, portions of the discharge head 28 and the outer shell 31 are illustrated in relation to said discharge grate 32, and the discharge ports 34, which extend therethrough.

With reference to FIGS. 3 through 5 of the drawings, such illustrate details of the means for separating the discharge of the mill 14 into two or more separate and distinct products and for returning unwanted portions of such discharge to said mill, without the use of external auxiliary apparatus, which is provided by the present invention.

With particular reference to FIG. 3 of the drawings, such illustrates the means herein provided for separating the mill discharge into two or more portions to facilitate the return of the unwanted portion, or portions, of said discharge to the mill for further processing. For the purposes of clarity and simplicity, the lifters 36, 37, and 38 have been shown without the cover plates that normally enclose them on the interior.

In FIGURE 3 the discharge ports 34 through which ground material passes from the interior of the mill 14 to the lifters 36 and 37 are shown in phantom, being located between lifters 38, 38a. Imperforate segments of grate section separate the zones defined by lifters 38, 38a and serve to hold back the charge within the mill 14 and form enclosed spaces bounded by the lifters 36 and 37, and 37 and 38, respectively.

For illustrative purposes, it has been assumed that it is desired to remove, from the mill 14, two fractions of material, more specifically, that material of a size minus three inches-plus two inches and minus ten mesh. For this application, ports 34 have been dimensioned to prevent the exit of any material of greater than three inch size; and the lifter 36 is perforated to allow passage of any material smaller than two inches. The lifter 37 is perforated, that is, preferably fitted with wire mesh screen, at mesh; the lifters 38 and 38a are imperforate. This foredescribed portion of the device is, of course, only a portion of a repeating pattern around the mill; and the mill 14 rotates in the direction shown in the drawing.

In the operation of the apparatus, the pocket served by ports 34, shown in phantom, adjacent segment 32 receives the minus three inch-plus two inch material, which is then elevated to trunnion level, by the lifter 36 as the first product. The pocket of the adjacent segment 35 receives the minus two inch-plus ten mesh material, which after elevating toward the center of the mill 14, is also discharged through the trunnion. The pocket behind grate section 39 discharges the minus ten mesh material, after elevating to trunnion level as a further product.

Several suitable arrangements exist for the discharge from two, or even more segmental pockets through the trunnion, to two, or more, separate delivery points, as shown in FIGURE 4.

One of these arrangements is shown in detail in FIG. 4 of the drawings. In said arrangement, concentric cylinders 41 and 42 form two discharge passages from the mill 14, said cylinder 42 being held in position within said cylinder 42 by the spiral spacer 43. Said spacer 43, in addition to supporting cylinder 42 within cylinder 41, also serves to assist fiow of the coarser material as a result of the rotation of the mill 14.

The end cover plate 44 includes the suitable openings 45 and 46 therein constructed in such as manner that portions of the discharge material, brought to this point by either of the lifters 37, 38, or 38a, will be discharged into their respective discharge passages. In the position shown in FIG. 4, material from the upper litter is discharged into passage P-1; and material from the lower lifter is discharged into passage P-2.

The return of unwanted or undesired material to the interior of the mill 14 may be accomplished by the provision of similar ports in the inner cover plates, together with suitable deflector plates to empty the contents of the corresponding pocket through these ports. It will be seen that numerous size separations and discharge separations can be accomplished in this manner through the appropriate groupings of grates, lifters, and plates.

By way of specific example, in the common case, where only one product, all minus a specified mesh, is required, such requires only that alternate lifters be perforated and non-perforated and that alternate grate sections, similarly, be perforated and non-perforated. Assuming, for the purposes of illustration, that an all minus ten mesh discharge from the mill is required, alternate grate sections could be constructed having three-eighths inch wide slotted perforations in order to protect the finer wire screening from damage from larger particles of the material. The lifter closing the downstream side of this pocket would be fitted with ten mesh wire cloth; and as a result of this construction, the minus three-eighths inch-plus ten mesh material would be returned to the mill 14 and the minus ten mesh material from the succeeding pocket would form the mine product.

The operation of the device is believed to be apparent from the foregoing.

I claim:

1. An autogenous grinding mill for reducing friable material, including a grinding chamber rotatably supported on a pair of axially aligned end journals, said chamber being bounded by a cylindrical mid-section wall having annular end wall portions extending radially inwardly substantially normal thereto, each connecting with a conical end wall portion extending axially outwardly from the respective annular wall portion, one said annular wall portion being an outlet wall and including grate means for the passage of crushed material axially outwardly therefrom, the combination end wall structure providing an unrestricted free-fall mid-section of extended axial length, for a mill of given axial dimension.

2. An autogenous grinding mill structure as claimed in claim 1 having an outer axial end chamber abutting said outlet wall and extending radially inwardly to a said supporting journal, at least one delivery passage extending axially outwardly through the journal from said chamber; and perforated lifter means extending inwardly from the outer periphery of said chamber to said delivery passage to provide selective inward passage for particles of predetermined minimum size.

3. An autogenous grinding mill structure as claimed in claim 2 including a plurality of separate passages extending through said journal, each having a perforated lifter member of preselected individual mesh size extending outwardly therefrom to the outer periphery of said end chamber adjacent said grate means, to transmit inwardly therefrom to the respective journal passages particulate ground material of a sufiicient size to pass over the mesh surface of the respective lifter, whereby grated delivery of material is provided.

4. An autogenous grinding mill structure as claimed in claim 3 wherein said lifter members extend substantially radially inwardly within said end chamber.

5. An autogenous grinding mill structure as claimed in claim 4 wherein the conical end wall of the chamber opposite to said outlet wall includes a portion extending axially outwardly through the adjacent said journal, having an opening therein to define an inlet to the mill for said friable material.

6. An autogenous grinding mill structure as claimed in claim 5 wherein said annular Wall grate portion is constructed of relatively brittle material of high hardness, such as a nickel iron.

7. An autogenous grinding mill as claimed in claim 1 including an axially inwardly extending annular projection at the junction of said outlet grate wall with the respective said conical end wall portion, to provide additional protection to said grate from falling material.

8. An autogenous grinding mill structure as claimed in claim 2 including an axially inwardly extending annular projection at the junction of said outlet grate wall with the respective said conical end wall portion, to provide additional protection to said grate from falling material.

9. An autogenous grinding mill structure as claimed in claim 3 includingan axially inwardly extending annular projection at the junction of said outlet grate wall with the respective said conical end wall portion, to provide additional protection to said grate from falling material.

10. An autogenous grinding mill structure as claimed in claim 6 including an axially inwardly extending annular projection at the junction of said outlet grate wall with the respective said conical end Wall portion, to provide References Cited by the Examiner UNITED STATES PATENTS MacPhee 241179 Capen 241176 X Marcey 24170 X Bittner 241-176 X Willard 241181 Hardinge 241-70 Miller et a1. 241-181 X Miller 24170 X Weston 241-176 X Hardinge 241-26 Russel 24126 ANDHEW R. JUHASZ, Primary Examiner.

ROBERT C. RIORDON, Examiner.

additional protection to said grate from falling material. 20 H. F. PEPPER, Assistant Examiner. 

1. AN AUTOGENOUS GRINDING MILL FOR REDUCING FRIABLE MATERIAL, INCLUDING A GRINDING CHAMBER ROTATABLY SUPPORTED ON A PAIR OF AXIALLY ALIGNED END JOURNALS, SAID CHAMBER BEING BOUNDED BY A CYLINDRICAL MID-SECTION WALL HAVING ANNULAR END WALL PORTIONS EXTENDING RADIALLY INWARDLY SUBSTANTIALLY NORMAL THERETO, EACH CONNECTING WITH A CONICAL END WALL PORTION EXTENDING AXIALLY OUTWARDLY FROM THE RESPECTIVE ANNULAR WALL PORTION, ONE SAID ANNULAR WALL PORTION BEING AN OUTLET WALL AND INCLUDING GRATE MEANS FOR THE PASSAGE OF CRUSHED MATERIAL AXIALLY OUTWARDLY THEREFROM, THE COMBINATION END WALL STRUCTURE PROVIDING AN UNRESTRICTED FREE-FALL MID-SECTION OF EXTENDED AXIAL LENGTH, FOR A MILL OF GIVEN AXIAL DIMENSION. 